Just to note that for the idea of free will to make sense, then it cannot be built on a traditional materialist methodology because it negate how we view cause and effect. That doesn't mean it does not apply but that anyone touting it would have to accept that we would have an infinite number of uncaused causes so the idea of needing one to start it no longer makes sense. To be fair to Alan Burns, he sort of does accept the impact of this.
Over land above that what makes the very concept difficult is the point that Outrider has been making but I don't see much recognition of, in that if there is no action is not caused, what does that really mean? How do we will something without it being fully caused. If we have a set of choices and there is no or even partial cause, then what would make any decision more likely with it being free? It's not random in this definition so how could it be made. Removing cause and effect causes real problems for how this might happen